The series of experiments in this proposal is designed to provide a portion of the empirical data base that is needed to insure continuing progress in research using vaginal photoplethysmography. Variables relating to important probe characteristics will be examined as well as the crucial methodological variables of stimulus timing and sequencing. The effect of stimulus repetition and stimulus variation will be examined to provide information on the concept of sexual arousability. Sexual arousability is a concept of central importance in the development of models of human sexuality. There will be a concerted attempt to develop measurement conventions for vaginal photoplethysmography. This will include not only examination of the sensitivity of and relationships among various dependent variables, but also will include the examination of measurement artifacts associated with movement, muscle activity, and respiration. Finally, the vaginal photoplethysmographic response will be compared with the labial temperature response to evaluate the relative strengths and weaknesses of both measures. At all times there will be the effort to relate the field of genital measurement in women to other aspects of behavioral science. The successful completion of the proposed work would accelerate the development of clinical applications of vaginal measurement.